2Describing Chemical Reactions 11.1Describing Chemical ReactionsOn May 6, 1937, the huge airship Hindenburg erupted into a fireball. Within a short time, 210,000 cubic meters of hydrogen had burned and the airship was destroyed. The chemical reaction that occurred is “hydrogen combines with oxygen to produce water.” You will learn to represent this chemical reaction by a chemical equation.
3Writing Chemical Equations 11.1Writing Chemical EquationsWriting Chemical EquationsHow do you write a word equation?
4Writing Chemical Equations 11.1Writing Chemical EquationsWord EquationsTo write a word equation, write the names of the reactants to the left of the arrow separated by plus signs; write the names of the products to the right of the arrow, also separated by plus signs.Reactant + Reactant Product + Product
5Writing Chemical Equations 11.1Writing Chemical EquationsMethane + Oxygen Carbon dioxide + WaterThree common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.
6Writing Chemical Equations 11.1Writing Chemical Equationsiron + oxygen iron(III) oxideThree common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.
7Writing Chemical Equations 11.1Writing Chemical EquationsHydrogen Peroxide Water and OxygenThree common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.
8Writing Chemical Equations 11.1Writing Chemical EquationsChemical EquationsA chemical equation is a representation of a chemical reaction; the formulas of the reactants (on the left) are connected by an arrow with the formulas of the products (on the right).
9Writing Chemical Equations 11.1Writing Chemical EquationsHow do you write a skeleton equation?
10Writing Chemical Equations 11.1Writing Chemical EquationsWrite the formulas of the reactants to the left of the yields sign (arrow) and the formulas of the products to the right.
11Writing Chemical Equations 11.1Writing Chemical EquationsA skeleton equation is a chemical equation that does not indicate the relative amounts of the reactants and products.Here is the equation for rusting:Fe + O2 Fe2O3
12Writing Chemical Equations 11.1Writing Chemical EquationsA catalyst is a substance that speeds up the reaction but is not used up in the reaction.Without Catalyst With CatalystHydrogen peroxide decomposes to form water and oxygen gas. a) Bubbles of oxygen appear slowly as decomposition proceeds. b) With the addition of the catalyst manganese(IV) oxide (MnO2), decomposition speeds up. The white “smoke” is condensed water vapor.
13Writing Chemical Equations 11.1Writing Chemical Equations
14Writing Chemical Equations Animation 12Relate chemical symbols and formulas to the information they communicate.
18for Conceptual Problem 11.1 Problem Solving 11.2 Solve Problem 2 with the help of an interactive guided tutorial.
19Balancing Chemical Equations 11.1Balancing Chemical EquationsBalancing Chemical EquationsWhat are the steps in writing a balanced chemical equation?
20Balancing Chemical Equations 11.1Balancing Chemical EquationsTo write a balanced chemical equation, first write the skeleton equation. Then use coefficients to balance the equation so that it obeys the law of conservation of mass.
21Balancing Chemical Equations 11.1Balancing Chemical EquationsThis is a balanced equation for making a bicycle. The numbers are called coefficients—small whole numbers that are placed in front of the formulas in an equation in order to balance it.
22Balancing Chemical Equations 11.1Balancing Chemical EquationsA chemical reaction is also described by a balanced equation in which each side of the equation has the same number of atoms of each element and mass is conserved.
23Balancing Chemical Equations Simulation 11Sharpen your skills by balancing chemical equations.
3511.1 Section Quiz.1. Propane gas reacts with oxygen to produce water vapor and carbon dioxide. Choose the correct word equation for this reaction.propane + carbon dioxide water + oxygenpropane + oxygen + water carbon dioxidepropane + oxygen + water + carbon dioxidepropane + oxygen water + carbon dioxide
3611.1 Section Quiz.2. Which of the following is a skeleton equation?H2 + CO CH3OH2H2 + CO CH3OH2H2 + CO2 CH3OHhydrogen + carbon monoxide methanol
3711.1 Section Quiz.3. What coefficient for H2SO4 is required to balance the following equation?Ca3(PO4)2 + ____ H2SO4 3CaSO4 + 2H3PO41234